Process for removing naphthenic acids from mineral oils



United States Patent 3,222,275 PROCESS FOR REMOVING NAPHTHENIC ACIDS FROM MINERAL OILS William A. Krewer, Arlington Heights, Donald L. Klass,

Barrington, and George W. Ayers, Chicago, Ill., assignors, by mesne assignments, to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Filed July 13, 1964, Ser. No. 382,358 13 Claims. '(Cl. 208180) This invention relates to new and useful improvements and processes for the refining of crude petroleum fractions to reduce the amount of naphthenic acids present therein. This application is a continuation-in-part of application Serial No. 110,601 filed April 28, 1961, forfeited July 13, 1964.

Many crude oils contain sufiicient quantities of naphthenic acids to make it necessary to modify refining procedures in order that products such as lubricating stocks and lubricating oils be essentially free of acids. In the refining of crude petroleum which contains substantial amounts of naphthenic acids, there is a problem of excessive corrosion in the distillation equipment due to the production of hydrogen chloride by reaction of naphthenic acids in the petroleum with trace amounts of inorganic chlorides in solution. In the past, attempts have been made to remove naphthenic acids from crude petroleum or from petroleum fractions at various points in the refining processes, or to convert the naphthenic acids into salts or esters. Prior methods dealing with naphthenic acids have included neutralization by alkali esterification, catalytic decarboxylation of the acids, extraction with various phenols, alcohols, or other solvents, with or without neutralization, and clay treating. Numerous countercurrent solvent-extraction processes have been proposed for use in refining petroleum oils. One process which has been used utilizes an extracting solution consisting of an alkylolamine dissolved in .an aliphatic alcohol to react with and remove the naphthenic acids. Other methods have utilized esterification reagents to convert naphthenic acids into neutral esters which are left in the oil. Still another method which has been used for reducing the acidity of crude petroleumand petroleum fractions has utilized treatment with aqueous alkali to neutralize naphthenic acids, followed by separation of the aqueous solution of alkali metal naphthenate salts. This process, however, has been ineffective with many types of petroleum and petroleum fractions which contain high-molecularweight naphthenic acids, because the corresponding alkali metal naphthenates are oil-soluble and cannot be removed by washing with water.

It is therefore one object of this invention to provide an improved process for reducing the acid neutralization number of crude petroleum and petroleum fractions containing substantial amounts of naphthenic acids which form alkali metal salts which are oil-soluble.

Another object of this invention is to provide an improved process for refining crude petroleum and petroleum fractions containing substantial amounts of naphthenic acids in which the naphthenic acids are converted into polar derivatives which can be extracted in aqueous solution.

A feature of this invention is the provision of an improved process for reducing the acid neutralization number of crude petroleum and petroleum fractions containing substantial amounts of naphthenic acids by treatment with aqueous alkali and a compound selected from the group consisting of aliphatic sultones, carbyl sulfates, ethylene sulfates, propylene sulfates (wherein the heterocyclic carbon atoms may be part of an aromatic, cycloalkylene, cycloalkyl, alkylene, alkenylene, alkadienylene, arylene 3,222,275 Patented Dec. 7, 1965 and polyarylene group) and substituted derivatives thereof followed by water washing to remove the polar derivatives which are formed. These sulfur containing organic compounds may be represented by the following structural formulas:

sultones where A represents a carbon linkage of 3 to 5 carbon atoms, the bonds being attached to the end carbons of the linkage, of a hydrocarbon radical selected from the group consisting of alkylene, alkenylene, alkadienylene, arylene, polyarylnene, and C -C alkyl-, C -C alkenyl-, C -C aralkyl-, C C; cycloalkyland C -C aryl-substituted derivatives thereof.

D D 0 soz 0 0 s-o s ()2 Oz where R R R R R R are members selected from the group consisting of hydrogen, C C alkyl, C -C cycloalkyl, C -C aryl, C -C alkenyl, C C alkadienyl, C C alkaryl and C -C cycloalkyl formed by joining two alkyl groups attached to any two adjacent carbon atoms in said formula Methods of pareparing the alkylene sulfates employed in this invention may be found in Ham, Journal of Organic Chemistry, volume 25, page 864, 1960, and Brunken et al., Veroflentlichungen der Wissenschaftlichen Photo- Laboratorien-Agfa, volume 9, page 62, 1961. Methods of preparing the carb-yl sulphates may be found in an article by Bordwell et al., Journal of American Chemical Society, pages 3952-3955 (1954). Methods of preparing the sultones may be found in articles by Mustafa appearing in Chemical Reviews, volume 54, pages -223 (1954), and Organic Sulfur Compounds, N. Khar a'sch, editor (Pergamon Press, 1961), chapter 18.

Sultones are internal esters of hydroxysulfonic acids, from which they can be formed by loss of a molecule of water. They are generally 'fiveor six-membered ring compounds, with or without double bonds. Sultones have been prepared by a number of methods such as (1) treatment of an aliphatic olefin or cycloolefin with an S0 -dioxane addition compound, (2) treatment of a diolefin with an sO -dioxane addition compound and (3) heating (dehydration) of a hydroxysulfonic acid with sulfuric acid-acetic anhy dride mixture. In addition general modes ofpreparation are disclosedand taught in US. Patents 3,115,501 and 3,117,133.

Another feature of this invention is the provision of an improved process for reducing the acid neutralization number of crude petroleum containing substantial amounts of naphthenic acids, the alkali metal salts of [which are oil-soluble, in which the petroleum is treated with an aqueous alkali and a compound selected from the group consisting of aliphatic sultones, carbyl sulfates, ethylene sulfates, propylene sulfates, and substituted derivatives thereof, prior to treatment of the petroleum in the desalter, which removes the resulting polar derivatives of the naphthenic acids and naturally occurring salts from the treated petroleum.

Another feature of this invention is the provision of an improved process for reclaiming used crankcase oils in which the used oil is treated with a solid adsorbent to remove asphaltic and tarry materials, and then is treated with aqueous alkali and a sulfur compound having the aforedescribed generic structural formulas.

Other objects and features of this invention will become apparent from time to time throughout the specification and claims as hereinafter related.

This invention is based upon our discovery that naphthenic acids can be removed from crude petroleum or petroleum fractions by treatment with aqueous alkali and a compound selected from the group consisting of aliphatic sultones, carbyl sulfates, ethylene sulfates, propylene sulfates, and the substituted derivatives thereof, followed by Water washing. It is well known that naphthenic acids present in crude oil, and in petroleum fractions such as lubricating oils and lubricating oil extracts, are not readily removable by washing the oils with aqueous alkali solutions. In fact, the alkali naphthenates are soluble in oils to a much greater extent than they are in water. Since the acid neutralization number of crude oil and petroleum fractions is due largely to the presence of naphthenic acids, washing the oils with aqueous alkali solution is of little use for reducing the acid neutralization number because of the presence of high-molecular-weight naphthenic acids. We have found that the treatment of naphthenic acids with compounds selected from the group consisting of aliphatic sultones, carbyl sulfates, ethylene sulfates, propylene sulfates, and substituted derivatives thereof converts them into more polar products which have acidic properties and can be removed from the oil by water washing as the alkali metal salts. An increase in polar character of the naphthenic acids tends to make the acids and their alkali metal salts less soluble in the oil and more soluble in the water.

The sultones, represented by the generic structural formula O SO:

wherein A represents a carbon chain of 3 to 5 carbon atoms of a hydrocarbon radical of the group consisting of alkylene, alkenylene, alkadienylene, arylene and polyarylene may have other substituents as the following formulas indicate.

The carbyl sulfates, and ethylene sulfates represented y seamwhere R R R R R R are members selected from the group consisting of hydrogen, C -C alkyl, C -C cycl-oalkyl, C -C aryl, C -C alkenyl, (l -C alkadienyl,

"atoms in said formula are illustrated by the following non-limiting examples.

propylene sulfates Non-limiting examples of mono-valent alkyl-, alkenyl-, aralkyl-, aryl-, cycloalkyland alkaryl-substituents that may be present on any of the aforedescribed sulfur comounds include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl (or pentyl), isoamyl, hexyl, heptyl, octyl nonyl, decyl, hexenyl, heptenyl, octenyl, phenyl methyl, 2-phenyl butyl, Z-phenyl amyl, l-phenyl hexyl, 7- phenyl heptyl, naphthyl methyl, 2-naphthy1 butyl, anthryl methyl, 2-anthry1 methyl, phenyl, naphthyl, anthryl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, benzyl, tolyl, cresyl, etc. In the alkaryl or arylalkyl substituents, the aryl portion may have from 6-18 carbon atoms and the alkyl portion may have from 120 carbon atoms.

Other sultones useful in this invention are 4-hydroxy-2-butanesulfonic acid sultone; 4-hydroxybutanesulfonic acid sultone; propane sultone (3-hydroxypropanesulfonic acid sultone); 2,2,4-trimethyl-4-hydroxypentanesulfonic acid sultone; 2,S-dimethyl-3-hydroxybutanesulfonic acid sultone; 3,4-dimethyl-4-hydroxy-2-pentanesulfonic acid sultone; 2,2,4,4r-tetraphenyll-4-hydroxybutanesulfonic acid sultone; o-(hydroxymethyl)benzensulfonic acid sultone; l-propane sulfonic acid 3-hydroxysultone; l-butane sulfonic acid 4-hydroxys'ultone; l-butane sulfonic acid 3-hydroxys'ultone;

Z-butane sulfonic acid 4-hydroxysultone;

2-pentane sulfonic acid 4-hydroxysultone; l-pentane sulfonic acid S-hydroxysultone;

"2-methy1-2-pentane sulfonic acid 4-hydrox'ysultone,

3-methyl-4-heptane sulfonic acid 2-hydroxysultonc; and

the like. The sultones are soluble in hydrocarbon oils but insoluble in water. In general, the alkyl or cycloalkyl type v of sultone is more reactive than aromatic sultones in the reaction with naphthenic acids in the presence of aqueous caustic solution.

In carrying out this process, sufficient alkali metal hydroxide is added, as an aqueous solution, to neutralize the naphthenic acids present in the crude oil or petroleum fraction. A slight excess or alkali may be used, if desired, to insure complete hydrolysis of any excess of aliphatic sultone, ethylene sulfate, propylene sulfate, or carbyl sulfate that did not react with the alkali metal naphthenates. The ethylene sulfate, sultone, propylene sulfate, or carbyl sulfate (or derivatives thereof) is added to the oil in the proportion of one mol of reagent per mol of naphthenic acid present in the oil. The use of smaller proportion merely results in a decreased lowering of the acid neutralization number of the oil, while the use of a larger ratio results in unreacted organic sulfate or sultone remaining in the oil, which must be removed. Any alkali metal hydroxide may be used in this process, but sodium hydroxide is preferred. In carrying out this process, the oil being treated and reactants are contacted at ambient temperature, although any temperature up to about 200 F. may be used at which the materials are fluid. The order of addition of reagents is not critical in this process. If the organic sulfur compound is added first, an acid derivative is obtained which is neutralized by the alkali. If the alkali metal hydroxide solution is added first, the naphthenic acids are converted to oil-soluble alkali metal naphthenates which are converted to polar derivatives by reaction with the organic sulfur compound. Good contact of the oil with both the alkali metal hydroxide solution and the organic sulfur compound is very important for efiicient reduction of the acid neutralization number of the oil and satisfactory conversion of the napthenic acids. Where this process is used for reducing the acid neutralization number of a crude oil, the treatment is carried out prior to the desalting of the crude, and the aqueous layer containing the water-soluble naphthenic acid derivatives is removed in the desalter, with or without prior settling of the aqueous layer from the crude oil. When this process is used for recovery and reclaiming of used crankcase oils, the used oils are first filtered through a granular adsorbent to remove asphaltic and tarry impurities, and then treated with alkali metal hydroxide and the organic sulfur compound for removal of acidic components. The finished petroleum products which are obtained in this manner have low acid neutralization numbers, have increased resistance to oxidation and heat breakdown, and are more stable against color deterioration on extended storage. After addition of oxidation inhibitor and sludge dispersants they are equal to or even better than the unused oil containing the same additives.

The following non-limiting examples are illustrative of the scope of this invention.

Example 1 A lubricating oil extract (having an acid neutralization number of 6.5), obtained by phenol extraction of a lubricating oil fraction, was treated in accordance with the subject invention. A 100 g. portion of this lubricating oil extract (from the manufacture of 170 vis. neutral) was agitated for 30 minutes with a solution consisting of 0.46 g. of sodium hydroxide in 10 ml. water, while the temperature was gradually increased from room temperature to 167 P. Then 1.5 g. of ethylene sulfate was added and agitation continued for minutes. The mixture was Washed with water twice, then washed with dilute sulfuric acid, and finally washed with water until the washings were neutral to methyl orange indicator solution. After treatment, the oil had an acid neutralization number of 3.96. The naphthenic acids were removed with the aqueous phase in the form of polar derivatives.

Example 11 A mixture of 100 g. of lubricating oil extract obtained in the manufacture of 170 vis. neutral and 0.46 g. sodium hydroxide in 10 ml. water was agitated for 30 minutes while the temperature was gradually increased from room temperature to about 167 P. Then 1.3 g. of carbyl sulfate was added and agitation was continued for 15 minutes. The carbyl sulfate represented about 60% of the theoretical amount of organic sulfate required to react completely with the naphthenic acids in the oil. The mixture was Washed with water twice, then washed with dilute sulfuric acid, and finally washed with water until the washings were neutral to methyl orange indicator solution. The treated oil hand an acid neutralization number of 4.4. In the presence of caustic, one mol of carbyl sulfate reacts with one mol of naphthenic acid in the formation of polar derivatives. These naphthenic acid derivatives are sufficiently polar to be soluble in water and relatively insoluble in oil, and are thus removed by water Washing.

Example III When the process described in Examples I and II is repeated, substituting axyl, alkenyl, aralkyl, alkaryl, cycloalkyl and amyl derivatives of ethylene sulfate and carbyl sulfate in the treatment of acidic oils, the naphthenic acids are removed in the same manner. Likewise, the substitution of propylene sulfate or other derivatives of ethylene sulfate in the procedures of Example I results in the removal of naphthenic acids from the oil. Similarly, the substitution of alkyl derivatives of carbyl sulfate, i.e., carbyl sulfate with alkyl substituents such as methyl, ethyl, propyl, hexyl, decyl, etc., (substituents, on the ethylene chain), results in the formation of polar derivatives as in Example II which are structurally identical to the derivatives formed in that example except for the alkyl substituents.

Example IV When this process is applied to the treatment of acidic crude oils, the treatment is carried out prior to desalting of the crude. A 100 g. sample of a Texas crude oil having an acid neutralization number of 1.7 is treated in accordance with this invention. To this sample of crude, there is added 45 ml. of 3% aqueous sodium hydroxide with agitation. The mixture is agitated mechanically in a closed vessel at a temperature of F. for 15 minutes. At the end of this time, 3.8 g. of ethylene sulfate is added, representing one mol of ethylene sulfate per mol of naphthenic acid, and the mixture is agitated for 15 minutes at 130 F. After receiving this treatment, the crude oil is passed into an electric desalter, where the water-in-oil emulsion is broken, and water settles out as a separate layer containing dissolved naturally-occurring salts, and the napthenic acid derivatives produced by reaction with sodium hydroxide and ethylene sulfate. In carrying out this phase of the process, any one of the desalters which are conventionally used in breaking petroleum emulsions and removing salts is satisfactory. Examples of these desalters are well known in the art and can be found in Nelson, Petroleum Refinery Engineering, Fourth Edition, McGraw-Hill Book Company, pages 265- 268. Other types of equipment, e.g., settling tanks, filtration beds, etc., may be used in conjunction with or substituted for the electric desalter in our process for the reduction of acid numbers in crude oils. After removal of most of the naphthenic acid ethylene sulfate condensation products, and naturally-occurring salts from the crude oil, the acid number is reduced to about 0.3.

Example V A g. portion of a Texas crude oil having an acid neutralization of number of 1.7 is treated with 100 ml. of a 6% aqueous solution of potassium hydroxide. The mixture is mechanically agitated at 90 F. in a closed container for a period of 15 minutes to neutralize the naphthenic acids. To this mixture, there is added 5.7 g. of carbyl sulfate (one mole per mole of naphthenic acid), and agitation is continued at a temperature of F.

use) is not feasible.

for about minutes. At the end of this time, the crude oil is passed through a sand filter and then through an electric desalter, and is allowed to settle and separate into aqeous and oil phases. The aqueousphase is Withdrawn and contains most of the napthenic acid-carbyl sulfate condensation products and naturally-occurring salts from the crude oil. The crude oil has an acid neutralization number of 0.4 at the end of this period of treatment. If desired, the crude oil may be subjected to additonal washing to remove any remaining amounts of salts produced in this treatment.

Example VI Four hundred cc. of an East Texas crude oil having an acid neutralization of 0.6 (due to naphthenic acids contained therein) is placed in a steel bomb of approximately 1 liter capacity. After further addition of 0.6 gram propane sultone and of 0.5 gram of sodium hydroxide in 30 cc. of water, the bomb is closed and then rocked for three hours at 150 F. The bomb is then opened, the crude oil decanted from the bomb and washed with Water until the washings give no color to phenolphthalein indicator. The washed crude oil then has an acid neutralization number of 0.01. Practically all of the napthenic acids in the crude oil react with the propane sultone in the presence of aqueous alkali to give a product which dissolves in the water and is thus removed from the crude oil.

Example VII A 100-gram portion of lubricating oil extract having an acid neutralization number of 4.7 is agitated with a solution of 0.6 gram sodium hydroxide in 10 cc. of water and heated until the temperature of the mixture is 170 F. Then 1.1 grams of propane sultone is added and the agitation continued for twenty minutes. The oil layer is drawn off and washed three times with equal volume portions of hot water. The acid neutralization number of the washed oil is then 0.5.

Example VIII A IOO-gram portion of lubricating oil extract having an acid neutralization number of 4.7 is agitated and heated in a glass beaker until thetemperature is 160 P. Then 1.1 grams of propane sultone is added to the stirred oil and a solution of 0.6 gram sodium hydroxide in 10 cc. of water is added drop by drop. After addition of all of the sodium hydroxide solution to the mixture the agitation is continued and the temperature maintained at 160 F. for minutes. The oil layer is then separated from the aqueous layer and the oil is washed with hot water until the washings no longer give a red color with phenolphthalein indicator. The acid neutralization number of the washed oil is then 0.3.

Example IX The procedure of Example VHI is followed except that 1.3 grams of butane sultone (4-hydroxy-2-butanesulfonic acid sultone) is used instead of the 1.1 grams of propane sultone. The acid neutralization number of the washed oil is then 0.5.

While this invention is primarily concerned with the treatment of crude oil and virgin oil fractions, it is also applicable to the reclamation of used oils. Used oils, such as crankcase oils, have been reclaimed by various methods, including distillation to remove crankcase dilution, percolation through absorbents to remove asphaltic and tarry materials, and distillation over alkali to remove most of the organic acids. Where the oils contain a substantial amount of bright stock or other non-distillable lubricating fractions, it has been difiicult to reclaim all of the oil satisfactorily. When bright stock is present in the oil, distillation in the presence of alkali to remove acids (produced by partial oxidation of the oil during Thus, many reclaimed oils have relatively high organic acidities and may give trouble during usewith certain types of bearings. In the following example it is seen how this process can be applied to the production of reclaimed oils having low acid neutralization numbers and containing substantially no asphaltic or tarry material, regardless of whether bright stock is present in the oil.

Example X A used crankcase oil, black in color and having an acid neutralization number of 3.1 is percolated through fullers earth to remove asphaltic and tarry materials. The percolated oil is greenish-red in color and has an acid neutralization number of 0.7. A 1000 g. portion of the percolated oil is treated with 20 ml. of 3% sodium hydroxide at F. The mixture of oil and aqueous caustic is then mixed with 1.5 g. of ethylene sulfate and agitated and heated at F. for 15 minutes. The oil is then washed with successive portions of water until the washings are neutral to phenolphthalein indicator solution. The treated oil has an acid neutralization of about 0.08. This reclaimed oil has improved oxidation and color stability, and after addition of oxidation inhibitor and sludge dispersants to it, is equal to or even better than the unused oil containing the same oxidation inhibitor and sludge dispersants.

Examp-le'XI One hundred cc. of a used crankcase oil which had been percolated through fullers earth and then had an acid neutralization number of 1.1, is stirred and rapidly heated to F. with 0.35 gram of 4-hydroxybutanesulfonic acid sultone. The temperature is maintained at 180 F. and the stirring continued during the drop by drop addition of a solution of 0.6 gram sodium hydroxide in 10 cc. of water. The mixture is then stirred and heated for 20 minutes at 180 F. Finally, the oil layer is separated and washed repeatedly with hot distilled water until the washings no longer give a red color with phenolphthalein indicator. The acid neutralization number of the washed oil is 0.07. The reclaimed oil is suitable for reuse after addition of oxidation inhibitor and sludge dispersant additive.

The used crankcase oil which is treated in accordance with this process cannot be converted to a product having such a low acid neutralization number by merely percolating it through fullers earth, or by distillation in the presence of caustic, or by a combination of the two steps. This oil is only about 40% distillable in the presence of caustic Withoutsubstantial cracking.

Whenever it is desired to recover naphthenic acids or other acids removed from petroleum fractions by our process the water phase and washings, containing derivatives of the acids, are subjected to hydrolysis. When the aqueous phase and washings recovered in any of the foregoing examples are treated with mineral acid (e.g., HCl, H 50 etc.) the naphthenic acids are regenerated.

While we have described this invention fully and completely with special emphasis upon several preferred embodiments, we wish it to be understood that within the scope of the appended claims this invention may be practiced otherwise than as specifically described herein.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A method of removing naphthenic acids from a petroleum fraction which comprises mixing aqueous alkali metal hydroxide and a compound having a structural formula selected from the group consisting of where A represents a hydrocarbon linkage of 3 to 5 carbon atoms, the bonds being attached to the end carbons of the linkage, of a hydrocarbon radical selected from the group consisting of alkylene, alkenylene, alkadienyl- 1 1 ene, arylene, and polyarylene, and the C -C alkyl-, C C alkenyl-, C,C aralkyl-, C C cycloalkyland C C aryl-substituted derivatives thereof,

where D represents a member selected from the group consisting of ethylene and any two adjacent carbon atoms of a saturated hydrocarbon ring of -6 total carbon atoms and the C C alkyl-, C C alkenyl-, C -C aralkyl-, 07-03 alkaryl-, C -C cycloalkyland C -C aryl-substituted derivatives thereof, and

where R R R R R R are members selected from the group consisting of hydrogen, C C alkyl, C C cycloalkyl, C C aryl, C C alkenyl, C C alkadienyl, C C aralkyl, C -C alkaryl and C -C cycloalkyl formed by joining two alkyl groups attached to any two adjacent carbon atoms in said formula, with said petroleum fraction, removing the aqueous layer, and water washing the peroleum fraction to remove the reaction product therefrom.

2. A method of removing naphthenic acids from crude oil which comprises mixing the crude oil with aqueous alkali metal hydroxide and a compound selected from the group consisting of O-SO2 where A represents a hydrocarbon linkage of 3 to 5 carbon atoms, the bonds being attached to the end carbons of the linkage, of a hydrocarbon radical selected from the group consisting of alkylene, alkenylene, alkadienylene,, arylene, and polyarylene, and the C -C alkyl-, C -C alkeny1-, C7C33 ara1kyl-, C -C cycloalkyland C -C aryl-substituted derivatives thereof,

where D represents a member selected from the group consisting of ethylene and any two adjacent carbon atoms of a saturated hydrocarbon ring of 5-6 total carbon atoms and the C -C alkyl-, C -C alkenyl-, C7-C38 aralkyl-, C -C alkaryl-, C -C cycloalkyland C C aryl-substituted derivatives thereof, and

where R R R R R R are members selected from the group consisting of hydrogen, C -C alkyl, C -C cycloalkyl, C C aryl, C -C alkenyl, C -C alkadienyl, C -C aralkyl, C7-C35 alkary-l and C -C cycloalkyl formed by joining two alkyl groups attached to any two adjacent carbon atoms in said formula, prior to desalting, settling to remove a substantial portion of the aqueous phase, washing the treated crude oil with water, and se-parating the remaining aqueous phase from the treated and washed crude oil by desalting.

3. A method in accordance with claim 1 in which the alkali metal hydroxide and sulfur compound are added in substantially stoichiometric quantities for reaction with the naphthenic acids.

4. A method in accordance with claim 1 in which the reaction is carried out at about to 200 F.

5. A method in accordance with claim 1 in which the petroleum fraction is treated with sodium hydroxide and a compound of the formula:

6. A method in accordance with claim 1 in which the petroleum fraction is treated with sodium hydroxide and a compound of the formula:

7. A method in accordance with claim 1 in which the petroleum fraction is treated with sodium hydroxide and a compound of the formula:

Hz? (3H2 o 0 s 2 8. A method in accordance with claim 1 in which the petroleum fraction is treated with sodium hydroxide and a compound of the formula:

/CH2CE1 O 0H:

9. A method in accordance with claim 2 in which the crude oil is treated with sodium hydroxide and a compound of the formula:

GE -CH, 0 o \S/ 2 10. A method in accordance with claim 2 in which the crude oil is treated with sodium hydroxide and a compound of the formula:

where A represents a hydrocarbon linkage of 3 to 5 carbon atoms, the bonds being attached to the end carbons of the linkage, of a hydrocarbon radical selected from the group consisting of alkylene, alkenylene, alkadienylene,

' arylene, and polyarylene, and the C -C alkyl-, C -C 13 alkenyl-, C -C aralkyl-, C -C cycloalkyland C -C aryl-substituted derivatives thereof, v

02 where R R R R R R are members selected from the group consisting of hydrogen, C -'-C alkyl, C -C cycloalkyl, C -C aryl, C -C alkenyl, C -C alkadienyl,

C -C aralkyl, C -C alkaryl and C -C cycloalkyl formed by joining two alkyl groups attached to any two adjacent carbon atoms in said formula, with a petroleum fraction containing naphthenic acids, separating the aqueous phase from the oil phase, washing the petroleum fraction with water, and subjecting said water phase and washings to hydrolysis to release the naphthenic acids combined therein.

13. In a method of reclaiming used crankcase oil in which the used oil is percolated through a granular adsorbent to remove asphaltic and tarry materials, the improvement which comprises treating the percolated oil in accordance with claim 1 to remove acidic impurities.

References Cited by the Examiner UNITED STATES PATENTS 1,281,354 10/1918 Handy 208183 2,339,520 1/ 1944 Riesmeyer 208- 2,717,879 9/ 1955 Hodges 208263 PAUL M. COUGHLAN, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner. 

1. A METHOD OF REMOVING NAPHTHENIC ACIDS FROM A PETROLEUM FRACTION WHICH COMPRISES MIXING AQUEOUS ALKALI METAL HYDROXIDE AND A COMPOUND HAVING A STRUCTURAL FORMULA SELECTED FROM THE GROUP CONSISTING OF 